What do you think should happen if a player plays an illegal move in blitz not necessarily involving check and before he presses the clock his opponent replies with what appears to be checkmate ?

In practice I would have thought the result of a win would stand assuming the player delivering mate didn't claim the illegal move. If the player who made the illegal move or a watching arbiter points out the illegality, presumably the game restarts with a time penalty as stipulated by the new Laws. Interesting problem though, and one that could arise in practice.

What do you think should happen if a player plays an illegal move in blitz not necessarily involving check and before he presses the clock his opponent replies with what appears to be checkmate ?

In practice I would have thought the result of a win would stand assuming the player delivering mate didn't claim the illegal move. If the player who made the illegal move or a watching arbiter points out the illegality, presumably the game restarts with a time penalty as stipulated by the new Laws. Interesting problem though, and one that could arise in practice.

I don't think that's the case at all. If the player making the illegal move hasn't pressed the clock then he's entitled to take it back and replace it with a legal move, without penalty.

I'm pretty sure I've seen something further since the spring, but this is the English Chess Forum, not the English Chess Federation so you would be better sending a message to the Federation office. It is not mandatory for the ECF officers to post here, so whilst some may choose to do so there is a more correct channel of communication.

Kishan Pattni writes: We are pleased to also be running the London Qualifier of the UK open blitz championship on behalf of the ECF at Holland Park on Saturday 8th September (11am start!) For more info or to register please visit https://www.englishchess.org.uk/uk-open ... mpionship/